The International Astronomical Union (IAU) was founded in 1919. Its mission is to promote and safeguard the science of astronomy in all its aspects through international cooperation. Its individual members–structured into Divisions, Commissions, and Working Groups–are professional astronomers from all over the world, at the Ph.D. level and beyond, who are active in professional research and education in astronomy. As of June 2020. the IAU has 13,398 members.

The key activity of the IAU is the organization of scientific meetings. Every three years, the IAU holds a General Assembly, which offers six IAU Symposia, some 15 Focus Meetings, and individual business and scientific meetings of Divisions, Commissions, and Working Groups. Among the other tasks of the IAU are the definition of fundamental astronomical and physical constants; unambiguous astronomical nomenclature; promotion of education activities in astronomy; and informal discussion on the possibilities of future international large-scale facilities. The IAU also serves as the internationally recognized authority for assigning designations to celestial bodies and surface features on them.